my snapper wont drive on left side

I have a snapper yard cruiser with a 38 inch deck , it only drives on the right side , this is bad for a ztr , as if you only want to go in circles . checked the belt , and the idler pulley and spring , both seem to be working correctly . checked the joystick operation and it does move the lever on the left pump , forward and reverse . I can start the engine and engage the drive and the right side wheel moves correctly and fast , but the left side only creeps , have not found any access to a reservoir , where I can check for fluid or add any . I do know that the fan is spinning fast on that left pump , and I can turn the left drive wheel by hand , when it is not running and I don't seem to feel a lot of resistance , some but not a lot . I can not spin right side wheel , as it should be , because of hyd. pressure in pump , this is with the motor not running .can you help me go to the next step and diagnose my problem. also where can I go to get a break down of the drive assembly . thanks

Which model snapper do you own,, and any model information from the tag on the drive unit would be also very helpful..

It is an Eaton drive. Kind of like the EZT except they have fluid tanks on them just behind the pulley.